On 09/03, gregkh@xxxxxxxxxxxxxxxxxxx wrote:
>
> The patch below does not apply to the 3.10-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@xxxxxxxxxxxxxxx>.
Greg! Sorry for inconvenience.
Yes, as David has already explained, I forgot to mention that this is only
for those trees which which have already backported 0c740d0afc3b "introduce
for_each_thread() to replace the buggy while_each_thread()".
I promise, I'll read Documentation/stable_kernel_rules.txt again.
> ------------------ original commit in Linus's tree ------------------
>
> From 4449a51a7c281602d3a385044ab928322a122a02 Mon Sep 17 00:00:00 2001
> From: Oleg Nesterov <oleg@xxxxxxxxxx>
> Date: Fri, 8 Aug 2014 14:19:17 -0700
> Subject: [PATCH] vm_is_stack: use for_each_thread() rather then buggy
> while_each_thread()
>
> Aleksei hit the soft lockup during reading /proc/PID/smaps. David
> investigated the problem and suggested the right fix.
>
> while_each_thread() is racy and should die, this patch updates
> vm_is_stack().
>
> Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
> Reported-by: Aleksei Besogonov <alex.besogonov@xxxxxxxxx>
> Tested-by: Aleksei Besogonov <alex.besogonov@xxxxxxxxx>
> Suggested-by: David Rientjes <rientjes@xxxxxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx>
> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
>
> diff --git a/mm/util.c b/mm/util.c
> index 7b6608df2ee8..093c973f1697 100644
> --- a/mm/util.c
> +++ b/mm/util.c
> @@ -183,17 +183,14 @@ pid_t vm_is_stack(struct task_struct *task,
>
> if (in_group) {
> struct task_struct *t;
> - rcu_read_lock();
> - if (!pid_alive(task))
> - goto done;
>
> - t = task;
> - do {
> + rcu_read_lock();
> + for_each_thread(task, t) {
> if (vm_is_stack_for_task(t, vma)) {
> ret = t->pid;
> goto done;
> }
> - } while_each_thread(task, t);
> + }
> done:
> rcu_read_unlock();
> }
>
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